The present invention relates to a pump, particularly a plunger pump, having a crank mechanism which, in an oscillating manner, drives a plunger arranged in a housing and guided in a receiving device, and having a pump head fixed to the housing for guiding the pressurized fluid, the housing surrounding the crank mechanism and the plunger.
Plunger pumps exist which are used in the high-pressure water field because they have a compact construction and can be used in an operationally reliable manner at pressures between 100 and 3,000 bar. With respect to other pump constructions, such as rotating positive-displacement pumps, these plunger pumps have the advantage of a good energy efficiency. Also, they are capable of delivering also under difficult fluid conditions, such as high temperature, barely viscous and very viscous media as well as solid-charged liquids. The plunger pumps run relatively quietly, cause low vibrations and are relatively easy to maintain. It is a disadvantage in the case of these vertically arranged plunger pumps that oil is present in the lower housing part having the crank mechanism. In comparison to the upper housing area, this housing area has to be mounted by corresponding strippers or a suction space sealing whose installation requires high expenditures. For this purpose, the surface of the piston rod must be machined in order to accommodate a corresponding sealing ring.
It is therefore an object of the present invention to provide a pump, particularly a plunger pump of the initially mentioned type, in which a reliable sealing with respect to the lower housing space containing the crank mechanism is provided in a simple manner and which can be used also under extreme environmental conditions.
This object is achieved by the pump of the present invention.
If elastic sealing devices are fixed to the plunger which provide a pressure-tight sealing with respect to the lower housing space containing the crank mechanism, the plunger or a vertical sealing and guiding element fastened to the plunger no longer has to be guided in a receiving device with particularly high precision in order to generate a sealing with respect to the upper housing part. A machining of the surface of the plunger rod for sealing ring receiving devices, for example, can be eliminated, or a sliding ring or rotary shaft seal can be saved. In this case, the elastic sealing devices can be used, among other things, as a splash guard in order to avoid an admission of oil from the area of the crank mechanism into the upper housing part. Such a hermetic sealing-off of the lower housing part is advantageous particularly for chemical pumps, because such a medium- and water-jet-resistant sealing has so far only been possible by diaphragm pumps. In particular, when the fluid to be delivered contains dirt, is toxic, harmful, corrosive, explosive or combustible, the advantages of a hermetic sealing are important. When the fluid is poorly lubricating, a driving mechanism lubrication could be used without a corresponding sealing.
According to a preferred embodiment of the invention, a space is formed in the housing above the lower housing space and below the pump head. This space may be filled with air. This creates a clear separation between a fluid space in the pump head, the space which is filled with air, and the space of the crank mechanism containing oil.
The sealing device is preferably fastened to the plunger on one side and to the housing on the opposite side. The mounting is facilitated in this case by interior webs constructed on the housing which surround the plunger in a ring-shaped manner so that the sealing devices are only clamped onto this housing section. In order to have sufficient elasticity for the movement of the plunger, the sealing device can be constructed as ring-shaped or conical bellows. A conical construction of the bellows has the advantage that a buckling is prevented. The waves provided on the bellows should be provided in such a number that no fluttering will occur even at high stroke frequencies. In the case of a gas-tight construction of the sealing devices, the pump can be used in an extreme environment.
The plunger may be constructed in several parts in order to be able to clamp the sealing device to a lower plunger element. In the upper area, the plunger is received in a piston-type manner in a bush or receiving device for the plunger sealing.
According to another embodiment of the invention, the pump has several adjacent plungers and sealing devices with respect to a lower housing space are provided around each plunger. The several plungers can then be combined to form a common pump unit in order to provide a high delivery volume. The pump is therefore preferably constructed as a high-pressure plunger pump.
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.